210 "Physical Geography of 



railway line. In order to avoid repetition, I shall, when describing 

 the formation of the Canterbury plains, return to this interesting 

 subject. From the lower end of the gorge, the river continues 

 its south-east course, which it commences at the junction of the 

 "Wilberforce with the main branch, for 37-^- miles before it empties 

 itself into the sea, 18 miles to the west of Bank's Peninsula. I may 

 also mention, that below the junction of the two main branches no 

 streams of any consequence, excepting the Acheron, coming from the 

 north-north-east, join the Eakaia. The explanation of this absence of 

 tributaries is easily found, in the fact that the huge morainic and 

 fluviatile deposits of the Eakaia, even above the gorge, dip away from 

 the river, so that a stream like the Selwyn has some of its sources on 

 the high ground in the Eakaia valley, close to the gorge. When the 

 river enters the plains, this fan arrangement of fluviatile deposits below 

 the morainic walls, crossing from side to side, is still more conspicuous, 

 and consequently the surface water, instead of joining the river, flows 

 on the top of the fan away from it. 



The Eangitata. 



The river, the hydrographic basin of which next claims our attention, 

 is the Eangitata, and although that portion of the Southern Alps 

 proper which it drains is not so extensive as that at the head of the 

 "Waimakariri, next to be considered, it measuring scarcely ten miles 

 along the summits of the Southern Alps, yet we find that the mountains 

 there are not only of greater altitude ; but, also, that the secondary 

 ridges enclosing the system in question, are on both sides of such 

 dimensions, that for a number of miles they are scarcely inferior in 

 average altitude to the peaks in the central chain. The most southern 

 branch of the Eangitata is the Havelock, which issues from a glacier 

 of small proportions when compared with those at the head of the two 

 rivers previously described. After a few miles, the valley enlarges to 

 a, breadth of more than a mile, and continues so wide for about fourteen 

 miles to its confluence with the Clyde, having a nearly south-eastern 

 course, which the river, for nearly seventy-eight miles as measured in 

 a straight line, maintains to where it joins the ocean. The Havelock 

 receives, in its course, numerous tributaries from both sides, of which 

 the Forbes river, issuing from two glaciers that descend from Mount 

 Forbes, is the most important. 



